TABLE 2.

Properties of the four hypotheses H₀, H₁, H₂, and H₃

Model	Nesting structure	Selection pressures across strata	Selection pressures across mutation category	No. selection pressures	Description
H0	H0	Unity	Unity	0
H1	H1H0	Equal	Equal	1
H2	H2H1H0	Equal	Distinct	3
H3	H3H2H1H0	Distinct	Distinct	33

Nesting structures of the four models, variation in selection pressure between strata (mutation type), and variation between mutation categories (missense, nonsense, or splice) are indicated. The number of resulting selection pressures follows. Parameterizations are indicated in the final column.